1. Field of the Invention
The present invention relates to a device for sinking wells, applicable more particularly to sinking wells under conditions where the well is partially or totally filled with water during its sinking. The invention also provides a well sinking process using this device.
2. Description of the Prior Art
There already exist a number of devices for sinking vertical wells in different types of ground. Thus, a device is known for example described in U.S. Pat. No. 3 894 587 filed on the Dec. 7, 1973. This device comprises two rotary cutting heads rotating about two parallel axes in opposite directions so as to bring the spoil or excavated earth between the two heads, where it is sucked up into a discharge duct. Such devices, which are currently used, do not however allow a well to be sunk with simultaneous lowering of a casing. Furthermore, they are not practical for forming wells of any or varying lengths. In particular, with such devices it is also impossible to provide variations and in particular increases in length at the bottom of the well or at a certain distance between the bottom and the surface.
There exist also a number of devices which have a certain degree of automation and a certain performance level but they require the use of very high power, require very heavy and space consuming equipment and require the sinking operations to be stopped during the positioning of a casing element at the head of the well, so that, for wells of large dimensions or diameters, the sinking rates which may be reached are scarcely of the order of 1 meter per day.